US 6807653 B2 Abstract A recovery path designing circuit, a method and a program thereof capable of reducing necessary resources as much as possible when designing a recovery path in a pre-establishing-type failure-detected end switching system. The recovery path designing circuit comprises an optimization standard making means to set an objective function for minimizing a link cost, a recovery path forming condition generating means, a link capacity calculating condition generating means, an accommodating condition generating means, and an optimizing means to solve integer programming problems expressed by the objective function and constraint expressions generated by those means, thus obtaining an optimum recovery path.
Claims(36) 1. A recovery path designing multipoint-to-point circuit for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, comprising:
an optimization reference generating means for setting an objective function to minimize a link cost;
a recovery path forming condition generating means for generating a constraint expression to form a recovery path from a switching start node to an egress node;
a link capacity calculating condition generating means for generating a constraint expression to calculate a link capacity required of the respective links;
a link accommodating condition generating means for generating a constraint expression to accommodate the link capacity within a range of a given link capacity;
a forbidden link and node setting condition generating means for generating constraint expressions to set at least one unavailable forbidden node and link with respect to each recovery path; and
an optimizing means for solving integer programming problems expressed by the objective function set by the optimization reference generating means and constraint expressions generated by the recovery path forming condition generating means, the link capacity calculating condition generating means, the link accommodating condition generating means, and the forbidden link and node setting condition generating means.
2. The recovery path designing circuit as claimed in
3. The recovery path designing circuit as claimed in
4. The recovery path designing circuit as claimed in
5. The recovery path designing circuit as claimed in
6. The recovery path designing circuit as claimed in
the optimization reference generating means sets an objective function to minimize a link metric and a path metric in addition to the minimization of the link cost; and
the link capacity calculating condition generating means generates a constraint expression to calculate, with respect to each state, a link capacity in the case where a primary path and a recovery path share their necessary resource.
7. The recovery path designing circuit as claimed in
the optimization reference generating means sets an objective function to minimize a link metric and a path metric in addition to the minimization of the link cost; and
the link capacity calculating condition generating means generates a constraint expression to calculate, with respect to each traffic, a link capacity in the case where recovery paths of one primary path share their necessary resources.
8. The recovery path designing circuit as claimed in
the optimization reference generating means sets an objective function to minimize a link metric and a path metric in addition to the minimization of the link cost; and
the link capacity calculating condition generating means generates a constraint expression to calculate a link capacity in the case where each of all paths is provided with dedicated resources.
9. A recovery path designing multipoint-to-point circuit for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, comprising:
an optimization reference generating means for setting an objective function to minimize a maximum link load;
a recovery path forming condition generating means for generating a constraint expression to form a recovery path from a switching start node to an egress node;
a link capacity calculating condition generating means for generating a constraint expression to calculate a link capacity required of the respective links and the maximum link load;
a link accommodating condition generating means for generating a constraint expression to accommodate the link capacity within a range of a given link capacity;
a forbidden link and node setting condition generating means for generating constraint expressions to set at least one unavailable forbidden node and link with respect to each recovery path; and
an optimizing means for solving integer programming problems expressed by the objective function set by the optimization reference generating means and constraint expressions generated by the respective recovery path forming condition generating means, the link capacity calculating condition generating means, the link accommodating condition generating means, and the forbidden link and node setting condition generating means.
10. The recovery path designing circuit as claimed in
11. The recovery path designing circuit as claimed in
12. The recovery path designing circuit as claimed in
13. A recovery path designing multipoint-to-point method for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, comprising:
an optimization reference generating step for setting an objective function to minimize a link cost;
a recovery path forming condition generating step for generating a constraint expression to form a recovery path from a switching start node to an egress node;
a link capacity calculating condition generating step for generating a constraint expression to calculate a link capacity required of the respective links;
a link accommodating condition generating step for generating a constraint expression to accommodate the link capacity within a range of a given link capacity;
a forbidden link and node setting condition generating step for generating constraint expressions to set at least one unavailable forbidden node and link with respect to each recovery path; and
an optimizing step for solving integer programming problems expressed by the objective function set at the optimization reference generating step and constraint expressions generated at the recovery path forming condition generating step, the link capacity calculating condition generating step, the link accommodating condition generating step, and the forbidden link and node setting condition generating step.
14. The recovery path designing method as claimed in
15. The recovery path designing method as claimed in
16. The recovery path designing method as claimed in
17. The recovery path designing method as claimed in
18. The recovery path designing method as claimed in
an objective function to minimize a link metric and a path metric is set at the optimization reference generating step in addition to the minimization of the link cost; and
a constraint expression to calculate, with respect to each state, a link capacity in the case where a primary path and a recovery path share their necessary resources is generated at the link capacity calculating condition generating step.
19. The recovery path designing method as claimed in
an objective function to minimize a link metric and a path metric is set at the optimization reference generating step in addition to the minimization of the link cost; and
a constraint expression to calculate, with respect to each traffic, a link capacity in the case where recovery paths of one primary path share their necessary resources is generated at the link capacity calculating condition generating step.
20. The recovery path designing method as claimed in
an objective function to minimize a link metric and a path metric is set at the optimization reference generating step in addition to the minimization of the link cost; and
a constraint expression to calculate a link capacity in the case where each of all paths is provided with dedicated resources is generated at the link capacity calculating condition generating step.
21. A recovery path designing multipoint-to-point method for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, comprising:
an optimization reference generating step for setting an objective function to minimize a maximum link load;
a recovery path forming condition generating step for generating a constraint expression to form a recovery path from a switching start node to an egress node;
a link capacity calculating condition generating step for generating a constraint expression to calculate a link capacity required of the respective links and the maximum link load;
a link accommodating condition generating step for generating a constraint expression to accommodate the link capacity within a range of a given link capacity;
a forbidden link and node setting condition generating step for generating constraint expressions to set at least one unavailable forbidden node and link with respect to each recovery path; and
an optimizing step for solving integer programming problems expressed by the objective function set at the optimization reference generating step and constraint expressions generated at the recovery path forming condition generating step, the link capacity calculating condition generating step, the link accommodating condition generating step, and the forbidden link and node setting condition generating step.
22. The recovery path designing method as claimed in
23. The recovery path designing method as claimed in
24. The recovery path designing method as claimed in
25. A recovery path designing multipoint-to-point program for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, to have a computer execute:
an optimization reference generating process for setting an objective function to minimize a link cost;
a recovery path forming condition generating process for generating a constraint expression to form a recovery path from a switching start node to an egress node;
a link capacity calculating condition generating process for generating a constraint expression to calculate a link capacity required of the respective links;
a link accommodating condition generating process for generating a constraint expression to accommodate the link capacity within a range of a given link capacity;
a forbidden link and node setting condition generating process for generating constraint expressions to set at least one unavailable forbidden node and link with respect to each recovery path; and
an optimizing process for solving integer programming problems expressed by the objective function set in the optimization reference generating process and constraint expressions generated in the recovery path forming condition generating process, the link capacity calculating condition generating process, the link accommodating condition generating process, and the forbidden link and node setting condition generating process.
26. The recovery path designing program as claimed in
27. The recovery path designing program as claimed in
28. The recovery path designing program as claimed in
29. The recovery path designing program as claimed in
30. The recovery path designing program as claimed in
an objective function to minimize a link metric and a path metric is set in the optimization reference generating program in addition to the minimization of the link cost; and
a constraint expression to calculate, with respect to each state, a link capacity in the case where a primary path and a recovery path share their necessary resources is generated in the link capacity calculating condition generating process.
31. The recovery path designing program as claimed in
an objective function to minimize a link metric and a path metric is set in the optimization reference generating process in addition to the minimization of the link cost; and
a constraint expression to calculate, with respect to each traffic, a link capacity in the case where recovery paths of one primary path share their necessary resources is generated in the link capacity calculating condition generating process.
32. The recovery path designing program as claimed in
an objective function to minimize a link metric and a path metric is set in the optimization reference generating process in addition to the minimization of the link cost; and
a constraint expression to calculate a link capacity in the case where each of all paths is provided with dedicated resources is generated in the link capacity calculating condition generating process.
33. A recovery path designing multipoint-to-point program for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, to have a computer execute:
an optimization reference generating process for setting an objective function to minimize a maximum link load;
a recovery path forming condition generating process for generating a constraint expression to form a recovery path from a switching start node to an egress node;
a link capacity calculating condition generating process for generating a constraint expression to calculate a link capacity required of the respective links and the maximum link load;
a link accommodating condition generating process for generating a constraint expression to accommodate the link capacity within a range of a given link capacity;
a forbidden link and node setting condition generating process for generating constraint expressions to set at least one unavailable forbidden node and link with respect to each recovery path; and
an optimizing process for solving integer programming problems expressed by the objective function set in the optimization reference generating process and constraint expressions generated in the recovery path forming condition generating process, the link capacity calculating condition generating process, the link accommodating condition generating process, and the forbidden link and node setting condition generating process.
34. The recovery path designing program as claimed in
35. The recovery path designing program as claimed in
36. The recovery path designing program as claimed in
Description The present invention relates to a recovery path designing circuit, a method and a program thereof for designing an alternative path in a pre-establishing-type failure-detected end switching system. As a conventional communication network designing method, for example, there has been proposed a recovery path designing method for a path end switching system in which a path is switched at the origin thereof by Yijun Xiong and Lorne Mason, “Restoration strategies and spare capacity requirements in self-healing ATM networks”, INFOCOM'97, April 1997. FIG. 1 is a diagram showing an example of a result of design obtained on the basis of the conventional designing method. In FIG. 1, reference marks n In this example in FIG. 1, the alternative path p In the following, another prior arts related to the present invention are mentioned. In Japanese Patent Application Laid-Open No. 2000-22750, the applicant of the present invention has disclosed a technique, in a multipoint communication network designing method, to design a link capacity and a node capacity in a communication network on the premise of variation of traffic demands. This application does not directly teach, but touches on, the recovery path designing method for a pre-establishing-type failure detecting end switching system. In Japanese Patent Application Laid-Open No. HEI 11-215124, the applicant has disclosed a technique to accommodate traffic even if demand patterns are changed to some extent. In Japanese Patent Application Laid-Open No. 2001-36574, the applicant has disclosed a technique, when communication between an ingress node and an egress node of a network is performed on a communication line having tree structure, to build a communication link having tree structure with the minimum number of branches, which accommodates paths between a given entrance node and exit node. Additionally, in Japanese Patent Application Laid-Open No. 2002-57676, the applicant has disclosed a technique to permit arbitrary communication within a given range by providing the amount of data traffic flowing in through an ingress node and the amount of data traffic flowing out from an egress node. Compared to the path end switching system, in a failure-detected end switching system, there is no need to notify a failure occurrence because a node that has detected the failure switches a route, thus enabling faster failure recovery. However, a plurality of recovery paths are necessary for one primary path. Thereby, unless the recovery paths are set so as to effectively share the resources for recovery, a great amount of resources is to be required. The method proposed by Yijun Xiong and Lorne Mason is premised on the path end switching system. In this method, it is impossible to design recovery paths on the basis of failure-detected end switching, and an efficient recovery path designing method has been sought. It is therefore an object of the present invention to provide a recovery path designing circuit, a method and a program thereof capable of reducing necessary resources as much as possible when forming recovery paths on a pre-establishing-type failure-detected end switching system. According to a first aspect of the present invention, for achieving the object mentioned above, there is provided a recovery path designing circuit for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, comprising: an optimization reference generating means for setting an objective function to minimize a link cost; a recovery path forming condition generating means for generating a constraint expression to form a recovery path from a switching start node to an Egress node; a link capacity calculating condition generating means for generating a constraint expression to calculate a link capacity required of the respective links; a link accommodating condition generating means for generating a constraint expression to accommodate the link capacity within a range of a given link capacity; a forbidden link and node setting condition generating means for generating constraint expressions to set at least one unavailable forbidden node and link with respect to each recovery path; and an optimizing means for solving integer programming problems expressed by the objective function set by the optimization reference generating means and constraint expressions generated by the recovery path forming condition generating means, the link capacity calculating condition generating means, the link accommodating condition generating means, and the forbidden link and node setting condition generating means. According to a second aspect of the present invention, in the first aspect, the optimization reference generating means sets an objective function to minimize a link metric and a path metric in addition to the minimization of the link cost. According to a third aspect of the present invention, there is provided a recovery path designing circuit for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, comprising: an optimization reference generating means for setting an objective function to minimize a maximum link load; a recovery path forming condition generating means for generating a constraint expression to form a recovery path from a switching start node to an Egress node; a link capacity calculating condition generating means for generating a constraint expression to calculate a link capacity required of the respective links and the maximum link load; an optimizing means for solving integer programming problems expressed by the objective function set by the optimization reference generating means and constraint expressions generated by the recovery path forming condition generating means, the link capacity calculating condition generating means, the link accommodating condition generating means, and the forbidden link and node setting condition generating means. According to a fourth aspect of the present invention, in one of the first to third aspects, the link capacity calculating condition generating means generates a constraint expression to calculate, with respect to each state, a link capacity in the case where a primary path and a recovery path share their necessary resources. According to a fifth aspect of the present invention, in one of the first to third aspects, the link capacity calculating condition generating means generates a constraint expression to calculate, with respect to each traffic, a link capacity in the case where recovery paths of one primary path share their necessary resources. According to a sixth aspect of the present invention, in one of the first to third aspects, the link capacity calculating condition generating means generates a constraint expression to calculate a link capacity in the case where each of all paths is provided with dedicated resources. According to a seventh aspect of the present invention, there is provided a recovery path designing method for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, comprising: an optimization reference generating step for setting an objective function to minimize a link cost; a recovery path forming condition generating step for generating a constraint expression to form a recovery path from a switching start node to an Egress node; a link capacity calculating condition generating step for generating a constraint expression to calculate a link capacity required of the respective links; a link accommodating condition generating step for generating a constraint expression to accommodate the link capacity within a range of a given link capacity; a forbidden link and node setting condition generating step for generating constraint expressions to set at least one unavailable forbidden node and link with respect to each recovery path; and an optimizing step for solving integer programming problems expressed by the objective function set at the optimization reference generating step and constraint expressions generated at the recovery path forming condition generating step, the link capacity calculating condition generating step, the link accommodating condition generating step, and the forbidden link and node setting condition generating step. According to an eighth aspect of the present invention, in the seventh aspect, an objective function to minimize a link metric and a path metric is set at the optimization reference generating step in addition to the minimization of the link cost. According to a ninth aspect of the present invention, there is provided a recovery path designing method for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, comprising: an optimization reference generating step for setting an objective function to minimize a maximum link load; a recovery path forming condition generating step for generating a constraint expression to form a recovery path from a switching start node to an Egress node; a link capacity calculating condition generating step for generating a constraint expression to calculate a link capacity required of the respective links and the maximum link load; According to a tenth aspect of the present invention, in one of the seventh to ninth aspects, a constraint expression to calculate, with respect to each state, a link capacity in the case where a primary path and a recovery path share their necessary resources is generated at the link capacity calculating condition generating step. According to an eleventh aspect of the present invention, in one of the seventh to ninth aspects, a constraint expression to calculate, with respect to each traffic, a link capacity in the case where recovery paths of one primary path share their necessary resources is generated at the link capacity calculating condition generating step. According to a twelfth aspect of the present invention, in one of the seventh to ninth aspects, a constraint expression to calculate a link capacity in the case where each of all paths is provided with dedicated resources is generated at the link capacity calculating condition generating step. According to a thirteenth aspect of the present invention, there is provided a computer-readable recovery path designing program for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, to have a computer execute: an optimization reference generating process for setting an objective function to minimize a link cost; a recovery path forming condition generating process for generating a constraint expression to form a recovery path from a switching start node to an Egress node; a link capacity calculating condition generating process for generating a constraint expression to calculate a link capacity required of the respective links; a link accommodating condition generating process for generating a constraint expression to accommodate the link capacity within a range of a given link capacity; a forbidden link and node setting condition generating process for generating constraint expressions to set at least one unavailable forbidden node and link with respect to each recovery path; and an optimizing process for solving integer programming problems expressed by the objective function set in the optimization reference generating process and constraint expressions generated in the recovery path forming condition generating process, the link capacity calculating condition generating process, the link accommodating condition generating process, and the forbidden link and node setting condition generating process. According to a fourteenth aspect of the present invention, in the thirteenth aspect, an objective function to minimize a link metric and a path metric is set in the optimization reference generating process in addition to the minimization of the link cost. According to a fifteenth aspect of the present invention, there is provided a recovery path designing program for designing recovery paths in a multipoint communication network including a plurality of nodes and links that connect the nodes, which employs a pre-establishing-type failure-detected end switching system in which alternate paths for respective primary paths are pre-established and a node that has detected a failure switches the route from a primary path to a recovery path, to have a computer execute: an optimization reference generating process for setting an objective function to minimize a maximum link load; a recovery path forming condition generating process for generating a constraint expression to form a recovery path from a switching start node to an Egress node; a link capacity calculating condition generating process for generating a constraint expression to calculate a link capacity required of the respective links and the maximum link load; According to a sixteenth aspect of the present invention, in one of the thirteenth to fifteenth aspects, a constraint expression to calculate, with respect to each state, a link capacity in the case where a primary path and a recovery path share their necessary resources is generated in the link capacity calculating condition generating process. According to a seventeenth aspect of the present invention, in one of the thirteenth to fifteenth aspects, a constraint expression to calculate, with respect to each traffic, a link capacity in the case where recovery paths of one primary path share their necessary resources is generated in the link capacity calculating condition generating process. According to an eighteenth aspect of the present invention, in one of the thirteenth to fifteenth aspects, a constraint expression to calculate a link capacity in the case where each of all paths is provided with dedicated resources is generated in the link capacity calculating condition generating process. The objects and features of the present invention will become more apparent from the consideration of the following detailed description taken in conjunction with the accompanying drawings in which: FIG. 1 is a diagram for explaining a conventional recovery path designing method; FIG. 2 is a diagram for explaining a failure recovery system based on a pre-establishing-type failure-detected end switching; and FIG. 3 is a block diagram showing a configuration of a recovery path designing circuit according to embodiments of the present invention. Referring now to the drawings, embodiments of the present invention are explained in detail. The present invention is intended to design an optimum recovery path on a pre-establishing-type (pre-registering type) failure-detected end switching system in which recovery paths are pre-established and a node that has detected a failure switches paths. First, an explanation is given of the pre-establishing-type failure-detected end switching system referring to FIG. In FIG. 2, reference marks n In this example, the recovery paths p In the pre-establishing-type failure-detected end switching system, there is a need to reserve resources for recovery paths such as a link capacity to realize reliable switching at the time of failure occurrence. To achieve the purpose, the resources for recovery paths may be shared. For example, it is assumed that a resource “1” is required for each path. In FIG. 2, the primary path p FIG. 3 is a block diagram showing a configuration of a recovery path designing circuit to design recovery paths for multipoint communication according to the present invention. The recovery path designing circuit comprises an optimization reference generating means The recovery path designing circuit is included in a computer The recording medium and/or transmission medium The program is read out by the computer In the following, an explanation is given of the operation of the recovery path designing circuit (recovery path designing method) according to the present invention. Here are shown embodiments in terms of the above-described three approaches, respectively. First, an explanation is given of symbols used in the embodiments in common. These symbols are categorized into sets and elements, variables, and constants. Each symbol indicates the respective sets and elements as follows: N: the set of nodes; N Z Z L: the set of links; the respective elements are expressed as (i,j,k), which expresses the k-th link from a node i to a node j; D: the set of traffic demands; the respective elements are expressed as d; t w Each symbol indicates the respective constants as follows: v c π π g a a
w m η: a coefficient for adding weight between a link cost and a path metric. Each symbol indicates the respective variances as follows: x b b φ: a maximum link load. In the following, an explanation is given of embodiments of the present invention employing the above-described symbols. [First Embodiment] Hereat, an explanation is given of a case of sharing resources over a whole network as the first embodiment. The optimization reference generating means The recovery path forming condition generating means The above expression (2) is based on the concept of network flow by Iri, Konno, and Tone, “Optimization Handbook”. A flow of “1” is generated from a switching start node, and a flow of “1” is taken in an Egress node. The intermediate nodes store the flow. By this means, a path from the switching start node to the Egress node is formed. The link capacity calculating condition generating means The constraint expression (3) is a formula for calculating a usage capacity of the respective links. The first term of the left side represents a capacity (resources) required for a primary path, and the second term thereof represents a capacity (resources) required for a recovery path(s). A point is to set the expression with respect to each state. In each state, such indicator constants as:
are used to add a link capacity of a path only. The other point is to take the maximum value in the right side, thereby realizing the sharing. The link accommodating condition generating means
The forbidden link and node setting condition generating means Subsequently, the means
Basically, the condition that a next node is not to be used comprehends the condition that the next link is not to be used. However, when a switching start node is placed just before an Egress node, and when it is impossible to establish node-disjoint paths (paths that do not share the same nodes), etc., a condition such that the next link is not to be used is separately required in addition to the condition that the next node is not to be used. Lastly, the optimizing means [Second Embodiment] In the following, an explanation is given of a case where resources are shared over recovery paths of the same primary path as a second embodiment. The operation of the recovery path designing circuit according to this embodiment is the same as that of the first embodiment except for the operation of the link capacity calculating condition generating means The link capacity calculating condition generating means In this embodiment, the above expression (7) is established to calculate a link capacity (resources) required by respective traffic demands because resources are shared only over recovery paths of the same primary path. The above expression (8) is to calculate a link capacity (resources) by adding up the link capacities obtained with respect to each traffic demand. [Third Embodiment] In the following, an explanation is given of a case where resources are dedicated (seized), that is, where each of all paths is provided with dedicated resources) as a third embodiment. The operation of the recovery path designing circuit according to this embodiment is the same as that of the first embodiment except for the operation of the link capacity calculating condition generating means The link capacity calculating condition generating means When resources are dedicated, resources corresponding to the link capacity of all paths are reserved regardless of failure states. Accordingly, the above expression (9) is established to calculate the whole resources (whole link capacity) by adding up the resources (link capacities) required for all the paths. [Fourth Embodiment] In the following, an explanation is given of a recovery path designing circuit according to the fourth embodiment. According to this embodiment, minimization of a path metric is realized in addition to the minimization of a link cost, which is realized in the respective first to third embodiments. In this embodiment, the optimization reference generating means With regard to the constraint expressions, the same constraint expressions as in the first to third embodiments can be employed. Namely, there can be used the constraint expressions respectively corresponding to the three kinds of approaches in which resources are: shared over a network; shared over recovery paths of the same primary path; and dedicated. [Fifth Embodiment] In the following, an explanation is given of a recovery path designing circuit according to the fifth embodiment of the present invention. In this embodiment, minimization of a max load on a link is realized to implement load sharing. The optimization reference generating means
The link capacity calculating condition generating means <Manner—1> First, an explanation is given of a case where resources are shared over a network according to the first manner of the fifth embodiment. The link capacity calculating condition generating means <Manner—2> In the second place, an explanation is given of a case where resources are shared over recovery paths of the same primary path according to the second manner of the fifth embodiment. The link capacity calculating condition generating means <Manner—3> Lastly, an explanation is given of a case where resources are dedicated according to the third manner of the fifth embodiment. The link capacity calculating condition generating means In the fifth embodiment, along with the change of the placement of the variations, the link accommodating condition generating means
With regard to the other constraint expressions, the same constraint expressions as in the first embodiment can be employed. Incidentally, the above-described embodiments are examples of preferred embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and modified embodiments may be implemented without departing from the scope of the present invention. As set forth hereinbefore, according to the present invention, recovery paths can be designed on the pre-establishing-type failure detected end switching system. This is because recovery path problems for the pre-establishing-type failure-detected end switching system are solved as integer programming. Especially when resources are shared over a primary path(s) and recovery paths, an accommodation rate at a traffic demand can be improved. While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention. Patent Citations
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